页岩气储层自吸–水化损伤–离子扩散相关性试验研究

Experimental Research on the Correlation of Spontaneous Imbibition–Hydration Damage–Ion Diffusion in Shale Gas Reservoirs

丁乙 雷炜 刘向君 秦章晋 梁利喜 周吉羚 熊健

DING Yi LEI Wei LIU Xiangjun QIN Zhangjin LIANG Lixi ZHOU Jiling XIONG Jian

油气藏地质及开发工程全国重点实验室（西南石油大学）， 四川成都 610500 中国石化西南油气分公司石油工程技术研究院，四川德阳 618000 中国石油西南油气田分公司，四川成都 610041 中国石油西南油气田分公司勘探开发研究院，四川成都 610041

National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University), Chengdu, Sichuan, 610500, China Petroleum Engineering Technology Research Institute, Sinopec Southwest Oil & Gas Company, Deyang, Sichuan, 618000, China PetroChina Southwest Oil & Gas Field Company, Chengdu, Sichuan, 610041, China Exploration and Development Research Institute, PetroChina Southwest Oil & Gas Field Company, Chengdu, Sichuan, 610041, China

压裂液与页岩气储层接触后，诱发自吸、水化损伤及离子扩散等水岩反应，导致压裂液返排率低、矿化度高，对压裂改造效果与页岩气产出均有显著影响。目前对上述水岩反应已经开展了针对性研究，但自吸、水化损伤及离子扩散同步产生，对三者之间相关性的研究较缺乏，难以准确认识压裂液与页岩的相互作用，不利于压裂优化设计。为此，立足于室内试验手段，明确了不同条件下的页岩自吸、水化损伤及离子扩散规律及影响因素，系统分析了页岩自吸、水化损伤及离子扩散之间的定量相关性以及相互作用机制。研究结果显示：自吸、水化损伤及离子扩散具有同步响应特征，均在自吸前期发展显著，后续逐渐趋于稳定；自吸与水化损伤相互促进，使页岩吸水量增大；随页岩吸水量增大，离子扩散程度加剧，更多盐离子扩散进入压裂液，使压裂液活度降低，减弱页岩自吸与水化程度。研究成果深化了对压裂液与页岩相互作用的认识，为实现页岩气储层高效水力压裂改造提供了理论支撑。

The interaction between shale gas reservoirs and fracturing fluid triggers water–rock reactions, such as spontaneous imbibition, hydration damage, and ion diffusion, restulting in low flowback rate and high salinity, which have a huge impact on fracturing results and shale gas production. Currently, research on these water–rock reactions has been conducted. However, spontaneous imbibition, hydration damage, and ion diffusion simultaneously occur, and the research on relations among these water–rock reactions is not enough. As a result, it is not beneficial for a deep understanding of the interaction between fracturing fluid and shale and the optimization design of fracturing. Therefore, based on laboratory experiments, the law and influence factors of shale spontaneous imbibition, hydration damage, and ion diffusion with various conditions were determined. Investigations of quantitative correlation and interaction mechanisms among shale spontaneous imbibition, hydration damage, and ion diffusion were completed. Results indicated that these reactions had synchronous response features and were all strong in earlier stages and gradually became stable. Spontaneous imbibition and hydration damage exhibited mutual promotion, increasing shale imbibition amount. With the increment in imbibition amount, ion diffusion grew, pushing more saline ions into fracturing fluid and reducing the activity of fracturing fluid. Consequently, shale spontaneous imbibition and hydration degree were restricted. The outcomes deepen the understanding of the interaction between fracturing fluid and shale, providing theoretical support for efficient hydraulic fracturing in shale gas reservoirs.

国家自然科学基金青年项目“高温高应力深层页岩渗吸–水化耦合机制”（编号：42202194）、中国石油–西南石油大学创新联合体科技合作项目“降低长水平段井下复杂与事故的配套技术”（编号：2020CX040201）资助

https://doi.org/10.11911/syztjs.2023088